The present disclosure relates to processes for producing polymers and gas-phase polymerization of olefins in particular.
Gas-phase polymerization is a known process for producing polymers. Gas-phase polymerization production efficiencies move toward the maximization of the polymer production rate. When the volume of the gas-phase reactor is fixed, an increase of the reactor inventory is one approach toward production maximization. Reactor inventory can be increased by increasing the bulk density of the fluidized bed (i.e., increasing the fluidized bulk density).
Attempts to manipulate fluidized bed parameters for increased productivity carry a high degree of uncertainty. Control of the fluidized bed bulk density is complex and difficult. The bulk density of the fluidized bed is a complicated interplay between many operational parameters such as upper/lower bed pressure/weight; bed height; bed temperature; gas pressure, composition, and flow rate; particle morphology; bed settled bulk density; and fluidization regime. It is difficult to prepare a fluidized bed model that captures all these parameters and accurately predicts fluidized bulk density characteristics under actual operating conditions. Such uncertainty poses the risk of sheeting, chunking, fouling, bed collapse, and/or reactor shutdown. The benefit of polymer production maximization by way of manipulation of the fluidized bulk density is balanced against these risks.
Desirable would be a gas-phase polymerization process that increases the settled bulk density of the fluidized bed and simultaneously avoids sheeting, chunking, overheating, bed collapse, and/or reactor shutdown.